Professional Interests: numerical linear algebra, graph algorithms

Answered

Graph visualization adding white to my nodes. How to solve it?

I'd assume this problem will also happen with other graphics elements. Could you try the following code and let me know if you'r...

Graph visualization adding white to my nodes. How to solve it?

I'd assume this problem will also happen with other graphics elements. Could you try the following code and let me know if you'r...

6 days ago | 1

| accepted

Answered

Shortest path through node group sets

There is no direct graph-based algorithm to solve this. I would suggest using the optimization toolbox to define this as an opti...

Shortest path through node group sets

There is no direct graph-based algorithm to solve this. I would suggest using the optimization toolbox to define this as an opti...

7 days ago | 1

| accepted

Answered

Error using 'graph' function in matlab R2019b

Could you try starting a new MATLAB and just enter the following code: >> A = ones(3); >> G = graph(A); If this gives the err...

Error using 'graph' function in matlab R2019b

Could you try starting a new MATLAB and just enter the following code: >> A = ones(3); >> G = graph(A); If this gives the err...

20 days ago | 0

| accepted

Answered

how to avoid floating point error and figure out a way to break out of this loop such that it generates correct answer

There has been a lot of research on how to deal with floating-point error in the Lanczos algorithm, see the Wikipedia page for s...

how to avoid floating point error and figure out a way to break out of this loop such that it generates correct answer

There has been a lot of research on how to deal with floating-point error in the Lanczos algorithm, see the Wikipedia page for s...

21 days ago | 0

Answered

Why my eigenvalues from (v,d)=eig(k,m) are so close to each other?

Since you mentioned eigenvalues converging at a certain number in the context of FEA analysis: This is usually not the case for ...

Why my eigenvalues from (v,d)=eig(k,m) are so close to each other?

Since you mentioned eigenvalues converging at a certain number in the context of FEA analysis: This is usually not the case for ...

21 days ago | 0

Answered

Does the function "ode45" use matrix decomposition?

ODE45 does not use a decomposition or solve a linear system with A. However, ODE15s and ODE23s, which are specialized for "stiff...

Does the function "ode45" use matrix decomposition?

ODE45 does not use a decomposition or solve a linear system with A. However, ODE15s and ODE23s, which are specialized for "stiff...

21 days ago | 0

| accepted

Answered

could anyone help me to calculate the euclidean distance for the matrix.

Hi Bruno, I have the same problem where I can't comment on your answer, so adding another answer here. That's a good point - ve...

could anyone help me to calculate the euclidean distance for the matrix.

Hi Bruno, I have the same problem where I can't comment on your answer, so adding another answer here. That's a good point - ve...

2 months ago | 0

Answered

could anyone help me to calculate the euclidean distance for the matrix.

For MATLAB R2017b or later, you can use the vecnorm function for a simpler construction than the one involving sqrt, sum, and .^...

could anyone help me to calculate the euclidean distance for the matrix.

For MATLAB R2017b or later, you can use the vecnorm function for a simpler construction than the one involving sqrt, sum, and .^...

2 months ago | 1

Answered

Hi just want to know if someone can maybe help me i have this matrix t want to get the eigenvector but it give me complex values and im pretty sure it must not be complex values for that matrix

A simple way to verify if the returned eigenvalues are correct is to compute both the eigenvalues and the eigenvectors, and to c...

Hi just want to know if someone can maybe help me i have this matrix t want to get the eigenvector but it give me complex values and im pretty sure it must not be complex values for that matrix

A simple way to verify if the returned eigenvalues are correct is to compute both the eigenvalues and the eigenvectors, and to c...

3 months ago | 1

Answered

How can I solve a sparse linear system efficiently in MATLAB?

Do you need the whole matrix A*inv(B)*A', or do you just need to apply this matrix to a vector (A*inv(B)*A'*x)? In the second ca...

How can I solve a sparse linear system efficiently in MATLAB?

Do you need the whole matrix A*inv(B)*A', or do you just need to apply this matrix to a vector (A*inv(B)*A'*x)? In the second ca...

3 months ago | 0

Answered

Backslash (\) operator became much slower when updating from 2015b to 2019a

Thank you for these logs. The difference in behavior comes from the following message, saying that we repeat the factorization w...

Backslash (\) operator became much slower when updating from 2015b to 2019a

Thank you for these logs. The difference in behavior comes from the following message, saying that we repeat the factorization w...

4 months ago | 1

| accepted

Answered

Backslash (\) operator became much slower when updating from 2015b to 2019a

Based on the spy plot, I would be astonished if a different method was selected between the two releases - I think the LU solver...

Backslash (\) operator became much slower when updating from 2015b to 2019a

Based on the spy plot, I would be astonished if a different method was selected between the two releases - I think the LU solver...

4 months ago | 1

Answered

Backslash error ''Warning: Matrix is singular to working precision."

For more details about what backslash does for sparse matrices, use spparms('spumoni', 1) cnew = Amat \ rhs; This will displa...

Backslash error ''Warning: Matrix is singular to working precision."

For more details about what backslash does for sparse matrices, use spparms('spumoni', 1) cnew = Amat \ rhs; This will displa...

5 months ago | 1

Answered

SVD freezes in 2018a

This sounds like a bug. It shouldn't be due to memory issues, SVD uses the same amount of memory if the matrix size and the synt...

SVD freezes in 2018a

This sounds like a bug. It shouldn't be due to memory issues, SVD uses the same amount of memory if the matrix size and the synt...

5 months ago | 0

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Answered

generalized eigen-problom, complex non-symmetric matrix, how to find orthogonal eigenvectors

There's an easier way to compute both U and W: [U, D, W] = eig(A, B); This will make sure that the eigenvectors U(:, i) and V(...

generalized eigen-problom, complex non-symmetric matrix, how to find orthogonal eigenvectors

There's an easier way to compute both U and W: [U, D, W] = eig(A, B); This will make sure that the eigenvectors U(:, i) and V(...

5 months ago | 1

Answered

Optimizing a matrix with cplexlp?

You can solve this using intlinprog. This is probably not the most efficient way of solving the problem, but reliable A = [0 1 ...

Optimizing a matrix with cplexlp?

You can solve this using intlinprog. This is probably not the most efficient way of solving the problem, but reliable A = [0 1 ...

5 months ago | 1

Answered

How SVD works for dimensionality reduction?

There's the svd function. The link points to the doc which has examples of how to use it.

How SVD works for dimensionality reduction?

There's the svd function. The link points to the doc which has examples of how to use it.

6 months ago | 0

| accepted

Answered

chol fails on Hermitian positive definite matrix?

That is astonishing. The matrix is not badly conditioned, I would expect CHOL to work fine here. I tried on my machine and didn...

chol fails on Hermitian positive definite matrix?

That is astonishing. The matrix is not badly conditioned, I would expect CHOL to work fine here. I tried on my machine and didn...

6 months ago | 0

| accepted

Answered

Sparsest solution for A\B

That statement is wrong, x = A\b doesn't return the solution x with the smallest number of nonzero elements. What mldivide does,...

Sparsest solution for A\B

That statement is wrong, x = A\b doesn't return the solution x with the smallest number of nonzero elements. What mldivide does,...

6 months ago | 2

| accepted

Answered

eigs function: incorrect eigenvalues

The problem is that the matrix A is badly conditioned: >> cond(full(A)) ans = 2.206837183464466e+16 This is just around...

eigs function: incorrect eigenvalues

The problem is that the matrix A is badly conditioned: >> cond(full(A)) ans = 2.206837183464466e+16 This is just around...

6 months ago | 2

Answered

Plotting eigenmodes in 3D

Depending on the format of your 3D-frame, maybe you could use pdeplot3d.

Plotting eigenmodes in 3D

Depending on the format of your 3D-frame, maybe you could use pdeplot3d.

6 months ago | 0

Answered

matchpairs function in r2019a

The algorithm solves the same problem as the Hungarian algorithm, but it's not the same algorithm. The Hungarian algorithm has c...

matchpairs function in r2019a

The algorithm solves the same problem as the Hungarian algorithm, but it's not the same algorithm. The Hungarian algorithm has c...

7 months ago | 0

| accepted

Answered

Hungarian algorithm realizated in matlab

As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

Hungarian algorithm realizated in matlab

As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

7 months ago | 0

Answered

Hungary algorithm

As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

Hungary algorithm

As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

7 months ago | 1

Answered

Matching of eigenvalues of 2 matrices

With R2018a, there is a new function matchpairs which might be useful for this. Basically, it takes a matrix of similarities bet...

Matching of eigenvalues of 2 matrices

With R2018a, there is a new function matchpairs which might be useful for this. Basically, it takes a matrix of similarities bet...

7 months ago | 0

| accepted

Answered

How to calculate n-th eigenvector using eigs() function

There's no way of doing this directly, and the indirect ways are hard to implement and not very robust. Also, this will be very...

How to calculate n-th eigenvector using eigs() function

There's no way of doing this directly, and the indirect ways are hard to implement and not very robust. Also, this will be very...

7 months ago | 2

| accepted

Answered

Simulating a Markov chain

There is a specific class that represents a discrete-time Markov chain in the Econometrics toolbox: dtmc.

Simulating a Markov chain

There is a specific class that represents a discrete-time Markov chain in the Econometrics toolbox: dtmc.

7 months ago | 0

Answered

Delete Highlighted Node in a Graph?

You can use highlight to set that marker to 'none'. The GraphPlot object h contains all the graphical properties of the plotted ...

Delete Highlighted Node in a Graph?

You can use highlight to set that marker to 'none'. The GraphPlot object h contains all the graphical properties of the plotted ...

7 months ago | 0

| accepted

Answered

Yet another lu(A) question and pivoting

I'm afraid I can't post the algorithm used in mldivide. Note that it's a bit more general: it also works if both the rows and th...

Yet another lu(A) question and pivoting

I'm afraid I can't post the algorithm used in mldivide. Note that it's a bit more general: it also works if both the rows and th...

7 months ago | 0

Answered

Yet another lu(A) question and pivoting

Yes, MATLAB checks if L is a permuted triangular matrix. See the doc for mldivide - Algorithm for full inputs. However, it's st...

Yet another lu(A) question and pivoting

Yes, MATLAB checks if L is a permuted triangular matrix. See the doc for mldivide - Algorithm for full inputs. However, it's st...

8 months ago | 1